Fuel injection control device



April 28; 1948. B. BOLLI v 2,398,878

FUEL INJECTION CONTROL DEVICE Filed Nov. 12, 1942 f, Ada; fiwhlq,

Patented Apr. 23, 194

. FUEL [INJECTION CONTROL DEVICE Switzerland, assignor to Bernhard Bolll, Arbon,

Adolph Saurer, Arbon.

Aktlengesellschaft Switzerland Application November 12, 1942, Serial No.

- In Germany October 24, 1941 3 Claims. (01. 123-140) This invention relates to internal combustion engines and more especially to means for controlling fuel injection in engines operating with spark-ignition, for instance aircraft engines, in I which a, fuel pump injects fuel into a space closely adjoining the working cylinder; or directly into the latter.

Fuel injection controls of this type are designed to supply to the weight of combustion air enclosed within the cylinder the required quantity of fuel. They operate as a rule in dependence upon the density of the charging air in front of the inlet valves.

wherein 125 is the pressure in front ofancl 17D the pressure in the narrowest part of the venturi, while 7 is the air density, 9 the acceleration of gravity and C the highest speed of air flow. The

difference in pressure ps-pn is thus proportional to the density of the charging air as long as the speed of flow C does not change, and it maybe used as a controlling agent for actuating the member that controls the quantity of fuel'injected by the fuel pump.

The quantity of air passing through-an internal combustion engine is dependent on the engine speed. The speed of flow inside the charging pipe is thus directly and in a linear degree dependent on the engine speed. Further, according to the invention, the speed of flow in the charging pipe and likewise in the venturi is maintained constant at varying speeds by means of a speed-responsive control member actuating a device arranged in the air current. which varies the cross-sectional area of the passage in such manner that the quantity of air passing per unit of time through the cross-sectional area of the venturi,i. e. the speed C, is not, or only slightly, varied throughout the entire range of engine speed.

In the drawing amxed to this specification and forming part thereof the invention is illustrated diagrammatically by way of example,

Fig. 1 being a side elevation, partly in axial section, of one embodiment in which the device for area of the passage varying the cross-sectional is located within the venturi, while Fig. 2 is a similar view of a second embodiment, in which thi device is inserted in a branch conduit arranged in parallel to the venturi.

Referring to the drawing and first to Fig. 1, l is the internal combustion engine, 2 the fuel injection pump, 3' a lever for adjusting the fuel delivery. Combustion air from the atmosphere enters the air supply conduit 4 at a pressure 113. In order to vary the engine output, the suction pressure ps can be lowered to the desired degree below atmospheric pressure by means of the throttle valve 5. The air flows through the venturi 6 arranged within the air conduit 4. The suction pressure 275 acts through the pipeJ l" on one side of a diaphragm (piston) 7, the pressure pain the venturi acts on the other side of the diaphragm through pipe! I. The two halves 8 and 9 of the diaphragmcasing form pressure chambers 9 and ID on opposite sides of the diaphragm. The latter is thus displaced in dependence upon the pressure drop ps-pn produced in theventuri, which drop, according to this invention, is proportional to the density. The displacement of the diaphragm istransmitted by the rod l3 to the lever 3 varying the quantity of injected fuel in such manner that with an increasing drop in pressure 1 5-4 1) of the venturi, i. e. with increasing density of the charging air, the quantity of fuel delivered rises. The spring l2 returns the rod l3 and the diaphragm 1 when the pressure difference drops.

The device for varying ,the cross-sectional area of passage in dependence upon the engine speed, according to the second feature of this invention, consists of a centrifugal governor l8 of a well known type driven by the engine and which, by means of a lever 2| engaging the governor sleeve l1, displaces the rod 20 and the control 'member l9 relative to the entrance of the venturi. This displacement occurs in such a manner that the control member I9 is moved into the venturi 6 when the engine speed drops, and is moved in the opposite direction, when the engine speed rises. The manner, in which the control member I9 is moved, and its shape, preferably as a profilated valve body, should be so chosen that with a constant density-vs in the suction pipe "nd at any engine speed the drop in pressure. Ds-Dn, i. e. the

least approximately, constant.

In the embodiment shown in Fig. 2 the combustion air is supplied to the pipe 6 by the charging blower 23, which is driven by the engine or by an exhaust gas turbine. The compressed air regulator 24 keeps the blower pressure p1. constant. The suction pressure ps may be lowered at will by means of a throttle 5.

The control member adapted to be adjusted in dependence upon the engine speed. here shown as a flap valve 29, and the venturi 8 are arranged in two parallel branches of the air conduit. The pressure drop produced in the nozzle 6 acts on a piston 25, which divides the cylinder 31 into the pressure spaces 26 and 21, and supplies the force for actuating the lever 3 for controlling. the quantity of fuel injected.

Here the adjusting movements dependent on the engine speed are brought about by a supply pump 3| driven by the engine, which aspires the fuel from a storage tank and delivers it through a conduit 32 to the fuel pump 2. In the conduit 32 a choke member 33 creates a pressure drop 271-172 in dependence upon the quantity of fuel passing therethrough. The delivery of the supply pump 3| and the pressure difference pl--p2 are directly dependent on the engine speed. The pressure diflerence acts on the piston 34 urging it together with the linkage 30 and the cam member 36 against the action of the return spring 35. The shape of the cam 36 determines the adjustment of the throttle 29, so that this throttle occupies a predetermined position for every speed.

instead of the supply pump, the lubricating pump, the cooling-water pump, the air pump 01 the like might be used. I

The flap 28 and cam member 36 might be replaced by a profilated valve.

' velocity of flow in the throttling portion, is, at

I I wish it to be understood that I do not desire to be limited to the exact details above described and shown in the drawing, for obvious modifications will occur to a person skilled in the art.

I claim:

1. An internal combustion engine comprising in combination, an engine cylinder, a fuel injection pump, means operatively connected with aid pump for controlling the quantity of fuel injected into said cylinder per working cycle, an air conduit communicating with said cylinder, an engine output regulating means, means responsive to changes in air density comprising a venturi arranged'in said air conduit between said regulating means and said ,engine, means for adjusting the total cross sectional-area of flow of air between said output regulating means and said engine, an engine-driven mechanism acting on said air flow adjusting means to reduce said cross sectional area in proportion, as the engine speed drops, in such manner as to render the speed of air flow in the narrowest portion of the venturi constant and independent of the engine weed, a casing, a piston-member in said casing dividing the casing in two chambers, one communicating with the narrowest part of said venturi, the other with the air conduit in front of the Venturi entrance and means arranged to transmit the movement of aid piston to said fuel-control means to adjust the the pump per working cycle in dependence upon the density of the air admitted.

2. The engine of claim 1, in which the air flow adjusting means is arranged inside the venturi.

3. The engine of claim 1, in which the air flow adjusting means is arranged in a branch air conduit connected in parallel to the venturi.

, BERNHARD BOLLI. 

